185509-32-4Relevant articles and documents
Phosphasalalen Rare-Earth Complexes for the Polymerization of rac-Lactide and rac-β-Butyrolactone
Liu, Hui,Shi, Xiaochao
, p. 705 - 717 (2021)
A series of new phosphasalalen pro-ligands, analogues of salalen but with an iminophosphorane replacing the imine functionality, and their corresponding rare-earth alkoxide and siloxide complexes were synthesized. The multinuclear NMR spectra and X-ray diffraction analyses revealed that, for the tert-butoxide and ethoxide complexes, the resulting phosphasalalen rare-earth product was composed of a mononuclear alkoxide and a binuclear complex containing bridged alkoxo and hydroxo groups, while an analogous binuclear complex was isolated as the sole product for the siloxide complex. All the complexes could catalyze the heteroselective ring-opening polymerization (ROP) of rac-lactide (Pr up to 0.77) with high catalytic activities and a controlled polydispersity. Remarkably, the yttrium and lutetium phosphasalalen complexes could also efficiently catalyze the ROP of rac-β-butyrolactone to produce syndiotactic polymers (Pr up to 0.73) while their salalen analogues were inert, revealing the special effects of the iminophosphorane moiety. Detailed end-group analyses and kinetic investigations suggested that the alkoxo-hydroxo-bridged complexes maintained their binuclear structures in the polymerization.
Yttrium phosphasalen initiators for rac-lactide polymerization
Clare,Cao, Thi-Phuong-Anh,Le Goff, Xavier F.,Long, Nicholas J.,Auffrant, Audrey,Williams, Charlotte K.
supporting information, p. 1475 - 1483 (2013/05/09)
A series of highly active yttrium phosphasalen initiators for the heteroselective ring-opening polymerization of rac-lactide are reported. The initiators are yttrium alkoxide complexes ligated by iminophosphorane analogues of the popular "salen" ligand, t
Synthesis and characterization of novel half-metallocene-type group IV complexes containing phosphine oxide - Phenolate chelating ligands and their application to ethylene polymerization
Liu, Jing-Yu,Liu, San-Rong,Li, Bai-Xiang,Li, Yan-Guo,Li, Yue-Sheng
body text, p. 4052 - 4059 (2011/10/03)
A series of novel half-metallocene-type group IV metal complexes containing phosphine oxide-phenolate chelating ligands of type CpMCl2[O-2R 1-4R2-6(Ph2P=O)C6H2] (Cp = C5H5, M = Ti, 2a: R1 = R2 = H; 2b: R1 = Ph, R2 = H; 2c: R1 = tBu, R2 = H; 2d: R1 = R2 = tBu; M = Zr, 3b: R1 = Ph, R2 = H; 3c: R1 = tBu, R2 = H; 3d, R1 = R2 = tBu) have been synthesized in high yields (60-76%) from CpMCl3 (M = Ti, Zr) with 1.0 equiv of 2R1-4R2-6(Ph2P=O)C 6H2OH in THF and in the presence of triethylamine, and the complexes were identified by NMR and mass spectra as well as elemental analysis. Structures for 2a-d and 3d were further confirmed by X-ray crystallography. Complexes 2a-d adopt a five-coordinate, distorted square-pyramidal geometry around the titanium center. Complex 3d has a six-coordinate, distorted octahedral geometry around the zirconium center, in which the equatorial positions are occupied by oxygen atoms of the chelating phosphine oxide-phenolate ligand and two chlorine atoms. The cyclopentadienyl ring and the oxygen atom of the THF molecule are coordinated on the axial position. When activated by modified methylaluminoxane, all complexes exhibited moderate to high activities toward ethylene polymerization, giving high molecular weight polymer with a unimodal molecular weight distribution. The substituents on ligands and the metal center as well as the reaction conditions have a profound effect on the polymerization. It should be noted that zirconium complexes 3b-d displayed notable ethylene polymerization activity even at high temperature (75 C). Moreover, using Ph3CB(C6F 5)4/i-Bu3Al in place of MMAO as a cocatalyst, 3b-d also generate high molecular weight polymer with high efficiency under the same conditions.
